1. Field of the Invention
The present invention relates to a thin-film semiconductor integrated circuit, a picture display device with using thereof, such as a liquid crystal display device, etc., and a manufacturing method thereof.
2. Description of Prior Art
In recent years, attention was paid upon a thin-film semiconductor integrated circuit, in which circuits are constructed by forming a plural number of thin-film transistors (hereinafter, abbreviated by xe2x80x9cTFTxe2x80x9d) on a single glass substrate. As an example of an application thereof can be listed up display devices, such as a liquid crystal display device, an EL (electro luminescence) display device, etc.
Conventionally, in particular, in a case of a picture display device, although a picture display portion of, such as pixel portions, etc., can be formed on a glass plate, however other portions for driving the picture display portion must be formed on an ordinary print circuit board, i.e., peripheral circuit portions, such as, a source driver, a gate driver, a shift register, a peripheral controller, etc., and this must be connected to the glass substrate by means of a cable terminal(s), thereby to be used. With such the method, there are pointed out drawbacks that the screen is small in sizes (i.e., from 4 inches to 10 inches), and that the costs also come to be high of the apparatus as a whole.
As a solution of such the drawbacks, it is possible to increase up the screen size greatly by forming the picture display portion and the driver, etc., on a signal substrate in one body, thereby to realize a picture display device, such as, a large screen wall hang television and/or monitor for a personal computer of high performances. However, for processing a large amount of information signals for a high-definition picture display portion, it is very important problem to improve driving capacities of the peripheral circuit portions, such as the driver, etc.
Accordingly, in order to improve the performances (in particular, electron mobility) of TFTs constructing the peripheral circuit portions, such as the driver, etc., extremely, it is necessary to prevent carriers from scattering on grain boundary by an improvement in a crystal property within an active region or area of those TFTs, and thereby to realize a high mobility.
However, for crystallization of Si film on the glass substrate, the crystallization must be performed under temperature being lower than a temperature (about 450xc2x0 C.) of generating distortion within the glass substrate, however the crystallization will not occur under such the low temperature, such as about 450xc2x0 C.
In recent years, as a means provided for dissolving such the problem, there are listed up a laser annealing method and a crystallization accelerating method, etc.
The laser annealing method is a one, wherein a amorphous crystalline or a fine crystalline Si thin-film, which is formed on the glass substrate by a decompression CVD method, etc., is melt and re-crystallized by using an eximer laser, and with this it is possible to form polysilicon Si having a particle diameter of around to 100 xcexcm under the temperature lower than 450xc2x0 C. However, axes of those crystals are in disorder and the surface scattering is large on the grain boundary which exists within the active region of the TFT, therefore, accompanying with this, the electron mobility comes to be large. For example, an electron effective mobility is about from 30 to 50 cm2/Vs (Japanese Patent Laying-Open No. Hei 9-27452 (1997)), and this is low comparing to that of the single crystal Si, about 500 cm2/Vs (S. M. Sze, Physics of Semiconductor Devices, P. 29, Second Edition, Wiley).
Also, in the Si thin-film on a insulator substrate having a high crystallizing temperature, a catalyst element introduction method is proposed as a means, for reducing down the crystallizing temperature thereof. For an example, a method wherein crystal nucleus is formed on the insulator substrate, on which is formed amorphous crystal silicon in a solid phase (Japanese Patent Laying-Open No. Hei 8-316485 (1996)), a method wherein on a polysilicon are formed accumulated layers of amorphous crystal silicon, on which is formed an exposed polysilicon, as the nucleus for a next crystal growth (Japanese Patent Laying-Open No. Hei 8-31749 (1996)), a method wherein a partially crystallized silicon thin-film is amorphous crystallized selectively by ion implantation while the remaining crystalline portion is grown into crystal, again as the nucleus (Japanese Patent Laying-Open No. Hei 10-55960 (1998)), a method of accelerating a speed of crystallization by means of diffusion of metal elements (Japanese Patent Laying-Open No. Hei 9-27452 (1997), Japanese Patent Laying-Open No. Hei 10-64819 (1998) and Japanese Patent Laying-Open No. Hei 11-186164 (1999)) and a method of varying irradiation energy and irradiation time in a manner of step-like (Japanese Patent Laying-Open No. Hei 10-97993 (1998)), etc.
In particular, in a case where a metal, such as Ni, etc., there is a problem that the metal added remains within the active region of the TFT, thereby decreasing down the performance of the TFTs extremely (in particular, a great increase in an Off current). As a means for dissolving such the problem, a high-temperature processing (600-900xc2x0 C.) is proposed, being so-called a gettering for removing the remaining metals therefrom. Because of this gettering temperature, the substrate to be used therein must be one of high cost, such as, quartz or crystallized glass, etc., having high temperature resistance, (for example, being disclosed in Japanese Patent Laying-Open No. Hei 11-87243 (1999), Japanese Patent Laying-Open No. Hei 11-186563 (1999), Japanese Patent Laying-Open No. Hei 11-191628 (1999), and Japanese Patent Laying-Open No. Hei 10-135469 (1998)), and as a result, there is an anxiety that it comes off the inherent object, i.e., a low-temperature process with low cost.
Furthermore, as another approach than the mentioned above, an idea is disclosed, wherein taking into the great consideration a high-speed operation characteristic, polysilicon germanium is used as the active layers of the TFTs, which construct the driver circuit and the signal processing circuit, in Japanese Patent Laying-Open No. Hei 11-251600 (1999).
Any one of those various methods for crystallization cannot be said to be a technology being fully complicated, therefore the maximum particle diameter attained is still small and a control is insufficient on positions of the crystal particles. It falls short of a practical size of about 8 xcexcm of the thin-film transistors, which are required for a liquid crystal panel of a large screen, and it is difficult to suppress unevenness or fluctuation in a distance between elements, due to positional shift of the crystal particles. Furthermore, directions of planes on the formed poly-crystal are in disorder, therefore the electron mobility depending upon the plane direction varies between the elements. Because of this, it does not comes up to a condition those technologies substitute the existing thin-film transistor devices.
An object, according to the present invention, is to provide an improved thin-film semiconductor integrated circuit device and a picture display device using thereof.
Also, another object, according to the present invention, is to provide a manufacturing method for manufacturing such the thin-film semiconductor integrated circuit device, easily and with good repetitiveness.
Explaining briefly on representative ones of various inventions disclosed in the present application, they are as follows:
Namely, according to one of the present invention, there is provided a thin-film semiconductor integrated circuit, comprising: a insulator substrate, such as of glass; a plural number of semiconductor single crystal portions accumulated on the insulator substrate, being divided and disposed in a matrix manner; and thin-film semiconductor circuit elements, each having activated region on a surface of that semiconductor single crystal portion. Further, those semiconductor single crystal portions disposed in the matrix-like manner in the vertical and horizontal directions are separated from each other through a crystal grain boundary therebetween, or separated through an amorphous crystalline or crystalline material or insulator.
Also, with the thin-film semiconductor integrated circuit device according to other present invention, those plural number of semiconductor single crystal portions are aligned regularly and periodically in the vertical and horizontal directions, wherein each surface of those shows (110) plane and each of the semiconductor single crystal portions is bonded in one body through the crystal grain boundary.
With such the structure, it is possible to realize the thin-film semiconductor integrated circuit device having superior electric characteristics, wherein a large number of TFTs, being equal in the characteristics (namely, each having uniform electric characteristics), are disposed on the insulator substrate of, such as glass, in the matrix-like manner, so as to be integrated in one body.
Further, by applying such the thin-film semiconductor integrated circuit device into a picture display portion and/or a peripheral circuit portion of a picture display device, it is possible to realize a picture display device of high performances. Namely, TFTs constructing the picture display portion and/or the peripheral circuit portion are formed upon surfaces of the single crystals where no crystal grain boundary exists, which are divided and disposed periodically, thereby maintaining high mobility for those TFTs, so as to enable the picture display portion and/or the peripheral circuit portion to operate at high speed, and further since the surfaces of those plural number of single crystals are disposed regularly in the matrix-like manner in the vertical and horizontal directions, then a fine and complicated thin-film circuitry can be formed on the insulator substrate of glass, etc., collectively, in the same manner as the ordinary LSIs, and also inner-wiring and cross-wiring can be formed easily, in the same manner.
For example, by applying the above-mentioned thin-film semiconductor integrated circuit device into the picture display portion, on which a large number of TFTs for use as pixels are disposed in the matrix-like manner at a high density, it is possible to obtain a remarkable effect therefrom.
On a while, it is also possible to apply the thin-film semiconductor integrated circuit device according to the present invention into TFTs constructing the peripheral circuit portion while forming TFTs constructing the picture display portion in amorphous crystalline semiconductor regions. In this instance, it is possible to improve the high speed operation of the peripheral circuit portion, and at the same time to ensure the displaying performance same to the conventional one, with which the Off current in the picture display portion can be reduced, thereby suppressing the fluctuation in nobilities between the TFTs for use of pixels.
Furthermore, it is needless to say that the thin-film semiconductor integrated circuit according to the present invention can be applied into both the picture display portion and the peripheral circuit portions.
Accordingly, in the picture display device, according to one of the present invention, in a first and a second semiconductor thin-film regions accumulated on a common insulator substrate are provided a first thin-film semiconductor circuit element for constructing a picture display portion and a second thin-film semiconductor circuit element for constructing a peripheral circuit portion for driving that picture display portion, wherein at least one of the first and the second thin-film semiconductor circuit elements, in particular, the active regions thereof are provided on the plural number of semiconductor single crystal portions, which are divided and disposed in a matrix-like manner in the first or the second semiconductor thin-film region corresponding thereto.
According to such the present invention, the picture display portion and the peripheral circuit portion, such as a driver, etc., can be formed in one body on one piece of common glass substrate, thereby providing a picture display device in cheap, but having high performances and a large screen area therewith.
Also, according to the present invention, in such the thin-film semiconductor integrated circuit, a crystallization accelerating material is adhered at each of lattice points in a matrix, upon a surface of the amorphous crystalline thin-film semiconductor layer, which is accumulated on an upper portion of an insulator for forming semiconductor circuit elements therein, and this thin-film semiconductor layer is treated with heating process, to be crystallized, thereby enabling a large-scaled production thereof, with relative ease.
Further, according to other method of the present invention, after partially adhering the crystallization accelerating material on one side of end portions of each of the plural number of amorphous crystalline semiconductor layers, each of which is accumulated on an insulator for forming the semiconductor circuit elements therein and has a long and narrow portion between the both end portions, they are treated by heating process, so as to form a semiconductor single crystal portion in the amorphous crystalline semiconductor layer, thereby forming the thin-film semiconductor integrated circuit device.
The concrete picture display device, according to the present invention, into which is applied the thin-film semiconductor integrated circuit device formed in accordance with this method, comprises a first and a second semiconductor thin-film regions formed on a surface of a insulator substrate, and a first thin-film semiconductor circuit element formed in the first semiconductor thin-film region, for constructing a picture display portion, and a second thin-film semiconductor circuit element formed in the second semiconductor thin-film region, for constructing a peripheral circuit portion for driving the picture display portion, wherein at least one of the first semiconductor thin-film region and the second semiconductor thin-film region is constructed with a plural number of third semiconductor thin-film regions, each of which is long and narrow in a form and separated from each other, and further each the third semiconductor thin-film region has a semiconductor single crystal portion, extending long and narrow on a surface thereof, in which the first or the second thin-film semiconductor circuit element is provided by bringing those semiconductor single crystal portions into active regions thereof.
As can be understood from the above explanation, the display device, according to the present invention, in particular, in the peripheral circuit portion of a driver or the like, in charge of process of a large amount of information and/or the picture display portion occupying a large area, uses the single crystallized regions as the active regions of the TFTs for constructing them, thereby achieving a display device having a high signal processing speed and/or a high display characteristic.
For example, crystal grains of the single crystal, each having a surface area equal or larger than an area occupied by the active region of TFT, are disposed in a manner of a matrix or periodically, so that the active area of each of TFTs is made of the single crystal, thereby it is possible to form the TFT, in which substantially the crystal grain boundary does not exists within the active area of the TFT, and further this is applied to the peripheral circuit portion, such as the driver, etc., necessitating a high speed operation, and/or the picture display portion, thereby realizing a display device of high performances.
Also, since forming the picture display portion and the peripheral circuit portion, such as the driver, etc., together with in one body, on a single insulator substrate, makes possible of forming a picture display device of high performances and a large size, therefore it is possible to realize a high performance picture display device, by introducing a means for using the forming processes of TFT appropriately, in conformity with the characteristics required by each portion.